/*
 * TextListLabel.java December 2012
 *
 * Copyright (C) 2012, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import java.lang.annotation.Annotation;

import wx.xml.simpleframework.xml.Text;
import wx.xml.simpleframework.xml.strategy.Type;

/**
 * The <code>TextListLabel</code> object is used to create a label
 * that will create a converter used to read free text. Free text is
 * text that exists between elements. An <code>ElementListUnion</code>
 * can be declared to consume text that exists between the individual
 * elements by declaring a <code>Text</code> annotation with it. In
 * such a declaration unstructured text can be processed.
 *
 * @author Niall Gallagher
 * @see wx.xml.simpleframework.xml.core.GroupExtractor
 */
class TextListLabel extends TemplateLabel {

    /**
     * This is the empty value that is declared for the annotation.
     */
    private final String empty;

    /**
     * This is the element list union label that is declared with this.
     */
    private final Label label;

    /**
     * This is the text annotation declaration on the element list.
     */
    private final Text text;

    /**
     * Constructor for the <code>TextListLabel</code> object. This is
     * used to create a label used for reading free text declared
     * between the elements of an element list union. Such a label
     * enables serialization and deserialization of unstructured XML.
     *
     * @param label this is the label that is declared with this
     * @param text  this is the text annotation delcaration
     */
    public TextListLabel(Label label, Text text) {
        this.empty = text.empty();
        this.label = label;
        this.text = text;
    }

    /**
     * This is used to acquire the <code>Decorator</code> for this.
     * A decorator is an object that adds various details to the
     * node without changing the overall structure of the node. For
     * example comments and namespaces can be added to the node with
     * a decorator as they do not affect the deserialization.
     *
     * @return this returns the decorator associated with this
     */
    public Decorator getDecorator() throws Exception {
        return null;
    }

    /**
     * This returns a <code>Collection</code> of element names. This
     * will typically contain both the name and path of the label.
     * However, if this is a union it can contain many names and
     * paths. This method should never return null.
     *
     * @return this returns the names of each of the elements
     */
    @Override
    public String[] getNames() throws Exception {
        return label.getNames();
    }

    /**
     * This returns a <code>Collection</code> of element paths. This
     * will typically contain only the path of the label, which is
     * composed using the <code>Path</code> annotation and the name
     * of the label. However, if this is a union it can contain many
     * paths. This method should never return null.
     *
     * @return this returns the names of each of the elements
     */
    @Override
    public String[] getPaths() throws Exception {
        return label.getPaths();
    }

    /**
     * This is used to provide a configured empty value used when the
     * annotated value is null. This ensures that XML can be created
     * with required details regardless of whether values are null or
     * not. It also provides a means for sensible default values.
     *
     * @param context this is the context object for the serialization
     * @return this returns the string to use for default values
     */
    @Override
    public String getEmpty(Context context) throws Exception {
        return empty;
    }

    /**
     * This method returns a <code>Converter</code> which can be used to
     * convert an XML node into an object value and vice versa. The
     * converter requires only the context object in order to perform
     * serialization or deserialization of the provided XML node.
     *
     * @param context this is the context object for the serialization
     * @return this returns an object that is used for conversion
     */
    @Override
    public Converter getConverter(Context context) throws Exception {
        Type type = getContact();

        if (!label.isCollection()) {
            throw new TextException("Cannot use %s to represent %s", type, label);
        }
        return new TextList(context, type, label);
    }

    /**
     * This is used to acquire the name of the element or attribute
     * that is used by the class schema. The name is determined by
     * checking for an override within the annotation. If it contains
     * a name then that is used, if however the annotation does not
     * specify a name the the field or method name is used instead.
     *
     * @return returns the name that is used for the XML property
     */
    public String getName() throws Exception {
        return label.getName();
    }

    /**
     * This is used to acquire the path of the element or attribute
     * that is used by the class schema. The path is determined by
     * acquiring the XPath expression and appending the name of the
     * label to form a fully qualified path.
     *
     * @return returns the path that is used for the XML property
     */
    public String getPath() throws Exception {
        return label.getPath();
    }

    /**
     * This method is used to return an XPath expression that is
     * used to represent the position of this label. If there is no
     * XPath expression associated with this then an empty path is
     * returned. This will never return a null expression.
     *
     * @return the XPath expression identifying the location
     */
    public Expression getExpression() throws Exception {
        return label.getExpression();
    }

    /**
     * This is used to acquire the dependent class for this label.
     * This returns null as there are no dependents to the element
     * annotation as it can only hold primitives with no dependents.
     *
     * @return this is used to return the dependent type of null
     */
    @Override
    public Type getDependent() throws Exception {
        return label.getDependent();
    }

    /**
     * This is typically used to acquire the entry value as acquired
     * from the annotation. However given that the annotation this
     * represents does not have a entry attribute this will always
     * provide a null value for the entry string.
     *
     * @return this will always return null for the entry value
     */
    @Override
    public String getEntry() throws Exception {
        return label.getEntry();
    }

    /**
     * This is the key used to represent this label. The key is used
     * to store the parameter in hash containers. Typically the
     * key is generated from the paths associated with the label.
     *
     * @return this is the key used to represent the label
     */
    public Object getKey() throws Exception {
        return label.getKey();
    }

    /**
     * This acquires the annotation associated with this label. This
     * is typically the annotation acquired from the field or method.
     * However, in the case of unions this will return the actual
     * annotation within the union group that this represents.
     *
     * @return this returns the annotation that this represents
     */
    public Annotation getAnnotation() {
        return label.getAnnotation();
    }

    /**
     * This is used to acquire the contact object for this label. The
     * contact retrieved can be used to set any object or primitive that
     * has been deserialized, and can also be used to acquire values to
     * be serialized in the case of object persistence. All contacts
     * that are retrieved from this method will be accessible.
     *
     * @return returns the field that this label is representing
     */
    @Override
    public Contact getContact() {
        return label.getContact();
    }

    /**
     * This acts as a convenience method used to determine the type of
     * the field this represents. This is used when an object is written
     * to XML. It determines whether a <code>class</code> attribute
     * is required within the serialized XML element, that is, if the
     * class returned by this is different from the actual value of the
     * object to be serialized then that type needs to be remembered.
     *
     * @return this returns the type of the field class
     */
    public Class getType() {
        return label.getType();
    }

    /**
     * This is used to acquire the name of the element or attribute
     * as taken from the annotation. If the element or attribute
     * explicitly specifies a name then that name is used for the
     * XML element or attribute used. If however no overriding name
     * is provided then the method or field is used for the name.
     *
     * @return returns the name of the annotation for the contact
     */
    @Override
    public String getOverride() {
        return label.getOverride();
    }

    /**
     * This is used to determine whether the annotation requires it
     * and its children to be written as a CDATA block. This is done
     * when a primitive or other such element requires a text value
     * and that value needs to be encapsulated within a CDATA block.
     *
     * @return this returns true if the element requires CDATA
     */
    @Override
    public boolean isData() {
        return label.isData();
    }

    /**
     * Determines whether the XML attribute or element is required.
     * This ensures that if an XML element is missing from a document
     * that deserialization can continue. Also, in the process of
     * serialization, if a value is null it does not need to be
     * written to the resulting XML document.
     *
     * @return true if the label represents a some required data
     */
    public boolean isRequired() {
        return label.isRequired();
    }

    /**
     * This is used to determine if the label is a collection. If the
     * label represents a collection then any original assignment to
     * the field or method can be written to without the need to
     * create a new collection. This allows obscure collections to be
     * used and also allows initial entries to be maintained.
     *
     * @return true if the label represents a collection value
     */
    @Override
    public boolean isCollection() {
        return true;
    }

    /**
     * This is used to determine whether the label represents an
     * inline XML entity. The <code>ElementList</code> annotation
     * and the <code>Text</code> annotation represent inline
     * items. This means that they contain no containing element
     * and so can not specify overrides or special attributes.
     *
     * @return this returns true if the annotation is inline
     */
    @Override
    public boolean isInline() {
        return label.isInline();
    }

    /**
     * This is used to determine if an annotated list is a text
     * list. A text list is a list of elements that also accepts
     * free text. Typically this will be an element list union that
     * will allow unstructured XML such as XHTML to be parsed.
     *
     * @return returns true if the label represents a text list
     */
    @Override
    public boolean isTextList() {
        return true;
    }

    /**
     * This is used to create a string used to represent this text
     * list label. This will basically create a string representing
     * the other label in addition to the <code>Text</code> label.
     *
     * @return this is used to build a string for the list label
     */
    public String toString() {
        return String.format("%s %s", text, label);
    }
}
